TOKYO • US Defence Secretary James Mattis said yesterday that the United States stands "100 per cent" with Japan, while on a visit meant to confirm the importance of the countries' security alliance.

"We stand firmly, 100 per cent, shoulder to shoulder with you and (the) Japanese people," he told Japanese Prime Minister Shinzo Abe.

"I wanted to make certain that Article Five of our mutual defence treaty is understood to be as real to us today as it was a year ago, five years ago, and it will be a year and 10 years from now," he said in remarks at the start of their meeting.

The article commits each country to repel attacks on the other, in Japan or any territories it administers.

Kyodo news agency, citing an unidentified Japanese government source, said Mr Mattis had confirmed that the US defence commitment extended to the disputed islands known as Senkaku in Japan and Diaoyudao in China.

Mr Mattis arrived from South Korea. His visit to the region marks the first overseas trip of any senior official from the administration of US President Donald Trump, who previously suggested that America's longstanding role in North-east Asia could change.

On the campaign trail, Mr Trump raised the possibility of Japan and South Korea arming themselves with nuclear weapons.

He also accused Seoul and Tokyo of not paying their fair share for the 47,000 US troops stationed in Japan and 28,500 in South Korea.

Mr Abe, who is set to hold a summit with Mr Trump in the US next week, also emphasised the importance of the alliance.

He said: "I do have a hope, and I am convinced, together with you and President Trump, we will be able to demonstrate the unwavering alliance between Japan and the United States - both to the public inside Japan as well as outside Japan."

He praised Mr Mattis, who is scheduled to meet Japan's Defence Minister today, as the right person for the job.

Mr Abe has repeatedly argued that Japan bears an appropriate share of the costs of the alliance, which he stressed benefits the US, Japan and the region.

Before leaving South Korea, Mr Mattis said a nuclear attack by North Korea would trigger an "effective and overwhelming" response.

He also said "any attack on the US or our allies will be defeated", in comments to reporters ahead of a meeting with his South Korean counterpart Han Min Koo.

Mr Mattis' remarks come amid concern that North Korea could be preparing to test a new ballistic missile, in what could be an early challenge for the Trump administration.

The US and South Korea yesterday reconfirmed their commitment to the planned deployment this year of a US missile defence system known as Terminal High Altitude Area Defence (Thaad).

Chinese Foreign Ministry spokesman Lu Kang yesterday reiterated China's opposition to Thaad, which he said would never change.

AGENCE FRANCE-PRESSE, REUTERS